Method and apparatus for the solidification of molten sulphur

ABSTRACT

A method and apparatus for the solidification of molten sulphur involves feeding a layer of molten sulphur onto the normally upper surface of a movable member such as a belt. The belt is provided with a surface to which is applied a thin layer of water which inhibits the adherence of solidified or partly solidified sulphur thereto during the cooling and solidification stages. One method of cooling the sulphur is accomplished by tilting the surface of the movable member at selected points along its length so as to cause the molten sulphur to flow transversely from one side of the surface to the other. Another cooling and solidifying method involves dipping or sequential dipping of the sulphur layer into a bath or series of baths of water arranged along the surface of the movable belt. A lamination of sulphur layers may also be formed by the application of overlapping layers on the initial layer.

United States Patent Ellithorpe et al.

[ METHOD AND APPARATUS FOR THE SOLIDIFICATION OF MOLTEN SULPHUR [72] Inventors: Ernest Ellithorpe; Ronald B. Fletcher, both of Calgary, Alberta, Canada [73] Assignee: Sulform Limited [22] Filed: April 21, 1970 [21] Appl. No.: 30,558

[30] Foreign Application Priority Data MOITEN SULPHUK [151 3,684,005 [4 1 Aug. 15, 1972 Primary Examiner-Charles Sukallo Attorney-Mason, Fenwick & Lawrence [5 7] ABSTRACT A method and apparatus for the solidification of molten sulphur involves feeding a layer of molten sulphur onto the normally upper surface of a movable member such as a belt. The belt is provided with a surface to which is applied a thin layer of water which inhibits the adherence of solidified or partly solidified sulphur thereto during the cooling and solidification stages. One method of cooling the sulphur is accomplished by tilting the surface of the movable member at selected points along its length so as to cause the molten sulphur to flow transversely from one side of the surface to the other. Another cooling and solidifying method involves dipping or sequential dipping of the sulphur layer into a bath or series of baths of water arranged along the surface of the movable belt. A lamination of sulphur layers may also be formed by the application of overlapping layers on the initial layer.

11 Claims, 6 Drawing Figures PATENTEDAUB 15 I972 SHEET 1 BF 2 INVENTORS ERNEST Q. ELLVTHORPE? Rona LD Bhemnsa Mes.

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ATTORNEYS PKTENTEDAUG 15 1912 SHEET 2 BF 2 INVENTORS EIzNes-r RELu'rHoaPE #Eounw B. FLETCHER BY Wmso-m W ATTORNEYS METHOD AND APPARATUS FOR THE SOLIDIFICATION OF MOLTEN SULPHUR This invention relates generally to a method and apparatus for the solidification of molten sulphur.

Broadly speaking, the present invention contemplates the feeding of molten sulphur on the normally upper surface of a movable member, the cooling and solidification of molten sulphur thereon and the dispatch and delivery of solid or partially solid sulphur formations of a predetermined size from said movable member.

Elemental sulphur is normally recovered initially by the Frasch process and by treatment of hydrogen sulphite bearing natural and industrial gases in molten form. Sulphur mined by the Frasch process, for example, is in a liquid state and must be solidified forshipment. Numerous methods have been proposed for the rapid solidification of molten sulphur, its handling and transportation in a safe and efficient manner but at the present time none has proved completely acceptable. Indeed, some of the present practices of delivering molten sulphur for storage, its actual method of storage and subsequent recovery for use, are so clearly inefficient and in need of improvement that they are inconsistent with the general standards of todays technology. Certain well known methods of sulphur storage and recovery are almost somewhat archaic in their nature and clearly indicate the need for improvement.

For example, by one largely used delivery and storage method, molten sulphur is poured into rectangular forms, usually about 18 inches in height and then allowed to cool and solidify. The form is then raised and the procedure repeated until a large solid block often with dimensions of about 100 feet by 500 feet is formed. When the sulphur is required for the market, the required amount must then be recovered from the large rock-like formation in which it is entrapped. The recovery process normally involves the steps of drilling, blasting, ripping, dozing and crushing in order to produce managable formations of, for example, three to four inches in length and breadth, for transportation and market requirements.

This procedure has many serious disadvantages in practice. It is firstly hazardous in that during the forming and solidification stages, it is necessary for workmen to handle hot molten sulphur. Since sulphur is a poor conductor of heat and an excellent insulator, hot pockets of molten sulphur are usually formed in the sulphur vat or pile and these pockets may remain in definitely by reason of the great insulation factor of the sulphur itself. The hot pockets are indeed a great hazard to manual workers during the recovery process and fatalities are known to have occurred as a result. Additionally, it must be recognized that although explosive blasting is normally quite hazardous the use of dynamite to blast areas of sulphur storage piles substantially increases the danger factor, for example, if sufficient density of the sulphur fines is developed as a result of an explosion and the critical heat density is developed at the same time, serious fires or indeed further explosions could well result. The ripping, dozing and crushing necessary in typical presently used recovery procedures creates a large amount of sulphur dust which frequently cause dangerous flash fires. In addition, the sulphur dust is very fine and of low density and readily carries on breezes of low velocity, thus also creating a problem of pollution.

It has been known for many years that sulphur can be solidified on stainless steel belts travelling over a network of spray nozzles for some 300 to 400 feet at velocities of 40 to 120 feet per minute. This method has proven itself capable of producing suitable sulphur flakes for the sulphur industry. However, it has also been proved to be very costly in comparison with the alternative method of vatting and subsequently blasting and crushing for recovery as previously outlined.

In view of the comparatively low cost of the process and apparatus of the present invention, and in the light of its high level of safety it could be immediately innovated to provide an acceptable solution to the main problems of sulphur solidification and recovery.

Therefore, it is an object of the present invention to overcome the significant problems existing in present day sulphur storage and recovery methods and provide a method and apparatus for the solidification and storage of sulphur which is both safe and efficient.

According to the broad aspects of the present invention, a method and apparatus for solidifying molten sulphur comprises feeding a layer of molten sulphur onto the normally upper surface of a movable member which is so surfaced as to inhibit adherence of solidified sulphur or partly solidified sulphur thereto during the cooling and solidification stages. The actual cooling of the sulphur may advantageously be accomplished by tilting the surface of the movable member at selected points along its length so as to cause the molten sulphur to flow transversely from one side of the surface to the other at and about those selected points. The transverse movement thus effected tends to subject the molten sulphur to a rolling action and expose a substantial portion of the body of the sulphur to direct air contact. Alternatively, cooling and solidification may be advantageously accomplished by simple dipping or sequential dipping of the sulphur layer into a bath or a series of baths of aqueous cooling medium arranged along the surface of the movable member. An additional layer or layers may be applied or fed onto the initial layer of sulphur to form a laminated solid sulphur structure but in this event the initial layer must be of sufficient thickness and strength to support the subsequently applied layer or layers.

Reference is now made to the accompanying drawings which illustrate preferred embodiments of the invention and in which;

FIG. 1 is a diagrammatic layout of one embodiment of the present invention incorporating the transverse belt tilting feature.

FIGS. 2a and 2b illustrate the manner in which the movable belt of this embodiment of the present invention may be tilted.

FIG. 3 is a diagrammatic illustration of a sequential dipping method and apparatus of the present invention.

FIG. 4 is a perspective view of one form of cooling ladder for molten sulphur.

FIG. 5 is a perspective view of a weir assembly over which molten sulphur may flow.

With reference to the drawings, FIG. 1 illustrates a sulphur cooling ladder generally at 10 which is structured to receive molten sulphur from delivery conduits by known means. It will be noted that the cooling ladder 10 is provided with vents or heat outlets 11 at each step of the ladder. Additional cooling of the molten sulphur may be affected at this stage of the method of the present invention by the direction of cooling air onto the molten sulphur as desired. The molten sulphur flows by gravity down the cooling ladder into a sulphur holding tank 12. A sulphur pump 13 is positioned to pump molten sulphur through conduit means 14. The molten sulphur may be released through sulphur discharge valve 15 onto weirs 16 and 16a. The weirs l6 and 16a are so structured to receive a predetermined volume of sulphur and deliver the liquid sulphur onto the surface of a movable belt disposed therebeneath when the volume of sulphur in the weirs has reached a predetermine level. A water bath 18 provides a supply of water which may be circulated by pump 19 through conduit means 20 to a water cooler 21. The cooled water may then be circulated through further conduit means 22 to a belt moistener 23 disposed above the surface of the moving belt 17. In this manner a thin film of water may be easily applied to the surface of the belt. The raised portions 24, 25, 26, 27 and 28 of the moving belt 17 serve to illustrate the alternate tilting sections of the belt 17 to provide transverse flow of the molten sulphur as it passes along on the belt 17. The assembly shown in FIG. 1 is such as to provide for two separate feeds of molten sulphur from weirs 16 and 16a. The separate feeds enable a second layer of molten sulphur to be applied to a first layer in overlapping relationship, thus providing a laminated formation of sulphur. Additional layers could, of course, be applied as required. FIG. 1 illustrates a slinger 29 which is a high speed belt capable of throwing the sulphur which has been solidified on the belt 17 distances of, for example, 75 and 100 feet onto a sulphur stock pile. At this particular point the sulphur is still in what is generally known as the green stage and thus breakage of the solidified sulphur is minimized.

FIGS. 2a and 2b illustrate an example of the manner in which the movable belt 17 may be tilted to ensure the alternate transverse flow of the molten sulphur. Suitable supporting structures which are not illustrated would be used to tilt or raise the belt to the desired angle. It is anticipated that as the sulphur cools and becomes more solidified a more steeply inclined tilt will be desired or possible in order to obtain the fullest desired cooling effect. It is anticipated, for example, that the tilts 26, 27 and 28 shown in FIG. 1 of the drawings may progressively increase to from four to 6 and to 8 inches at the highest point of their tilt on the edge of the belt 17. FIGS. 2a and 2b serve to illustrate the anticipated workable slopes or tilts in order to cause the molten sulphur to flow transversely on the belt.

In an alternative embodiment illustrated in FIG. 3, the molten sulphur is subjected to sequential dipping in baths 30 of an aqueous cooling medium such as water as it is moved longitudinally on the belt 17. A laminated sulphur layer may be formed by applying additional layers of molten sulphur through suitable sulphur delivery means indicated only diagrammatically at 31 in FIG. 3. The first layer of molten sulphur must have been cooled sufficiently to receive and support any additional or overlapping layers fed thereto at points 31 along the length of the belt 17. Pump 32 is adapted to circulate water through conduit means 33 to a water cooler 34 which may be provided with a fan 35 to facilitate the cooling thereof. The cooled water is then recirculated for reuse through conduit 36 to the water bath 37. Sizing cutters 38 are positioned to cut the solidified or partially solidified sulphur into sulphur formations of a predetermined size. The cut portions of sulphur may then be projected by the slinger 39 onto a sulphur stock pile which would normally be situated in the close proximity of the end of the apparatus.

In operation and in practice it is found that molten sulphur may advantageously be delivered onto the cooling ladder 10 for preliminary cooling before it is subjected to the solidification process on the belt 17. Heat is quickly released from the molten sulphur as it is allowed to fall by gravity down the steps of the cooling ladder 10 and is delivered into the tank 12. If the molten sulphur is still too hot by the time it reaches the tank 12, it may be re-circulated for a further passage down the cooling ladder 10 before it is subjected to solidification treatment. 7

A decision may be taken to re-circulate the sulphur if it is, for example, at a temperature of more than about 260 when it is delivered to the tank 12. Advantageously the molten sulphur should be as cool as possible before it is delivered onto the belt 17. If substantial heat is removed from the sulphur before it reaches the belt 17 it will be easier to handle and solidify and as much heat as possible should, therefore, be removed from the sulphur before it is delivered to the belt. The molten sulphur is normally processed at starting temperatures of from 245 to 325 F.

Although the belt 17 may be of stainless steel or other similar material for the purpose of practising the embodiments of FIG. 3 it would nevertheless be necessary to use a belt of more flexible material such as a tough heat-resistant rubber for the practice of the embodiment FIG. 1. It is clear that the material used for the belt of FIG. 1 should be such that it will permit fiexibility to the extent of permitting the raised or angled sections of the belt as shown in FIGS. 2a and 2b to ensure the transverse movement of the molten sulphur.

It is believed that an average of 11 tons per hour at a belt speed of feet per minute is satisfactory in the practice of the present invention. Tests were conducted at this speed for approximately 164 hours and practically no wasteage of sulphur was encountered. The time taken from feeding to recovery of the solid formed sulphur was about 1% minutes. The length of the belts 17 of the present invention are about feet long and approximately 36 inches wide and it was found that advantageously water may be used at aboutl gallon per minute which, by controlled delivery, provides a water film of about l/64 of an inch or less on the surface of the moving belt.

It will be seen from FIG. 1 of the drawings that the valves 15 and 15a are adjusted to permit enough sulphur to enter the weirs 16 and 16a to keep them filled up to the appropriate level. The excess molten sulphur over-flows the lips of weirs 16 and 16a and discharges a uniform thin film of molten sulphur onto the moving belt 17 disposed therebeneath. For good results the flow of the molten sulphur should be constant and the speed of the belt 17 so timed as to enable the formation of the desired thickness of film.

The formation of a lamination of sulphur is not absolutely essential to the present invention. It is believed that satisfactory cooling may be achieved with the transverse flow method disclosed in FIG. 1. However, if it is desired to form laminations provision is made for the delivery of a plurality of films of molten sulphur. In the embodiment of FIG. 1, for example, the two separate films may be advantageously delivered through control of the sulphur flowing from the valves and 15a into the weirs 16 and 16a. Similarly, in FIG. 3 the sulphur control will be developed from the points 31 along the length of the moving belt 17.

It is believed that when molten sulphur is fed and formed in a plurality of overlapping separate layers on the supporting belt 17 and cooling permitted between the application of each layer, that a larger part of the sulphur solidifies to the amorphous state. It is also believed that the shrinkage of the sulphur in the longitudinal direction of the belt 17 aids in freeing the solid sulphur from the surface thereof. However, the provision of a thin film of water or other aqueous medium on the belt when using the transverse flow method of FIG. 1 will inhibit any substantial adherence of the solid sulphur to the belt 17 and, in addition, the shrinkage of the solid sulphur will itself assist in the freeing of the solid sulphur from the belt 17.

When it is desired to form a laminated layer of sulphur the weir valves 15 and 15a may usefully be so controlled as to provide layers of about /a of an inch on the moving belt 17. In the use of the sequential dipping method of FIG. 3 each applied layer is cooled by dipping in the baths 30 before the next layer is applied in overlapping relationship to the previous layer. A laminated sheet of solidified sulphur may thus be produced usefully of about of an inch thick. It is preferable to ensure that the belt 17 is always suitably wetted with a thin film of water or other suitable aqueous medium. The absence of the thin film of water could well cause a temperature rise in the belt if it were composed of rubber or like material and consequently induce adherence between the sulphur and the rubber and in turn preventing the belt from being satisfactorily cleaned. Since solidified sulphur has a very high insulating quality during lamination, the first layer of, for example, A; of an inch of solid sulphur prevents a great amount of the expelled heat from the subsequent layers from entering or affecting the belt 17 The protection thus provided by the initial layer is adequate to eliminate the aforementioned problems of heat degradation between the sulphur and the belt. However, this is a problem which is not believed to be as significant in the transverse flow method of FIG. 1. In that particular method the body of sulphur is moved transversely and a substantial portion of it is quickly subjected to contact with the air and thus the heat of the sulphur is believed to more quickly dissipate, thereby substantially minimizing the problem of heat on the belt.

When the sulphur has been solidified it may be subjected to a cutting treatment such as may be provided by the sizing cutters 38. At this stage in the process the sulphur is in the amorphous stage. There is substantially no crystallization and no appreciable dusting or fines development as a result of the cutting. The sulphur still has a significant temperature at this stage, but it is at a point of solidification which is suitable for convenient cutting and delivery through, for example, the slinger 39, to a nearby stock pile. It may be noted from FIG. 1 that the cut pieces of sulphur progress up an inclined section 39 of the belt 17 which allows any excess water to drain off and for additional drying a fan 35 is disposed immediately over the inclined section to expel any remaining moisture from the sulphur.

As previously indicated water from the bath may be continuously pumped through the cooler 34 to dissipate the heat acquired from cooling the sulphur. It should be noted that the cooler 34 may have the dual purpose of dissipating heat from the coolant and also dryingthe product as indicated.

The rate of sulphur through-put in accordance with the invention is determined by the belt width. Most generally a width of 48 inches would have a capacity of 20 long tons per hour accepting the molten sulphur at any temperature between 250 and 310 F. Requirements of water or other coolant would be that amount necessary to offset normal evaporation.

In some installations the method and apparatus of the present invention may be operated in an environment which is open to the elements. If the conditions are satisfactory this kind of operation can be advantageous in terms of facilitating the cooling of the sulphur such as when a cooling breeze of low velocity is blowing. However, when the system is operated in direct contact with hot sun it has a marked retrograde effect on the cooling of the sulphur and the method is less efficient and more costly to run. In many instances, therefore, it would be considered advantageous to enclose the apparatus shown in FIGS. 1 and 3 in a housing which would be such as to close the apparatus from the outside elements so that it operates in a controlled environment. The housing would also be preferably arranged to provide space at the side of the belt for the manual operators of the system.

The methods and apparatus envisaged by the present invention overcome the serious economic and hazardous draw-backs of known sulphur treating systems in the prior art and present a new concept in sulphur treatment, which should benefit the industry generally.

We claim:

1. A method of solidifying molten sulphur comprising the steps of:

feeding a layer of molten sulphur onto a moving support surface which is so surfaced as to inhibit firm adherence of solidified sulphur thereto;

laterally tilting the support surface at selected points along its length so as to cause the molten sulphur layer formed thereon to flow transversely alternately from one side to the other;

providing a cooling bath of aqueous medium in contact with said surface;

moving said support so as to pass the layer of molten sulphur through the cooling bath to facilitate cooling and eventual solidification of the sulphur, and removing the cooled sulphur from said surface.

2. A method as claimed in claim 1 wherein the layer of molten sulphur is sequentially contacted a plurality of times with said cooling bath.

3. A method as claimed in claim 1 including the step of partially cooling said molten layer by contact with said bath and thereafter applying at least one additional layer of molten sulphur in substantially overlapping relationship to the first layer, subsequently cooling said additional layer so as to form a solid lamination of sulphur layers.

4. A method as claimed in claim 2 including the step of partially cooling said molten layer by contact with said bath and thereafter applying at least one additional layer of molten sulphur in substantially overlapping relationship to the first layer, subsequently cooling said additional layer so as to form a solid lamination of sulphur layers.

5. A method as claimed in claim 1 including the step of forming on the support surface a thin film of water sufficient to inhibit the firm adherence of molten sulphur thereto.

6. A method as claimed in claim 2 including the step of applying to the support surface a thin film of water sufficient to inhibit the adherence of solidified sulphur thereto.

7. A method as claimed in claim 1 wherein the molten sulphur is first subjected to a preliminary cooling step by being delivered onto a cooling ladder and allowed to flow downwardly by gravity thereon prior to being fed onto said support surface.

8. A method as claimed in claim 2 wherein the molten sulphur is first subjected to a preliminary cooling step by being delivered onto a cooling ladder and al lowed to flow downwardly by gravity thereon prior to being fed onto said support surface.

9. A method as claimed in claim 1 including the additional step of directing cooling air onto the surface of the molten sulphur prior to contact of the sulphur with the cooling bath.

10. A method as claimed in claim 1 including the step of directing cooling air onto the sulphur subsequent to its contact with said cooling bath.

1]. A method of solidifying molten sulphur comprising the steps of:

feeding molten sulphur onto a cooling ladder and allowing the molten sulphur to flow downwardly by gravity thereon into a holding tank disposed therebeneath;

selectively withdrawing molten sulphur from said holding tank and applying a layer thereof to the normally upper surface of a moving belt, said surface being provided with a thin layer of water sufiicient to inhibit the adherence of solidified sulphur thereto;

laterally tilting the support surface at selected longitudinally spaced points to cause transverse flow of the molten sulphur alternately from one side of the surface to the other;

passing said layer of molten sulphur sequentially through a cooling bath to facilitate cooling and solidification of the molten sulphur; and

removing solidified or partially solidified sulphur from said surface. 

2. A method as claimed in claim 1 wherein the layer of molten sulphur is sequentially contacted a plurality of times with said cooling bath.
 3. A method as claimed in claim 1 including the step of partially cooling said molten layer by contact with said bath and thereafter applying at least one additional layer of molten sulphur in substantially overlapping relationship to the first layer, subsequently cooling said additional layer so as to form a solid lamination of sulphur layers.
 4. A method as claimed in claim 2 including the step of partially cooling said molten layer by contact with said bath and thereafter applying at least one additional layer of molten sulphur in substantially overlapping relationship to the first layer, subsequently cooling said additional layer so as to form a solid lamination of sulphur layers.
 5. A method as claimed in claim 1 including the step of forming on the support surface a thin film of water sufficient to inhibit the firm adherence of molten sulphur thereto.
 6. A method as claimed in claim 2 including the step of applying to the support surface a thin film of water sufficient to inhibit the adherence of solidified sulphur thereto.
 7. A method as claimed in claim 1 wherein the molten sulphur is first subjected to a preliminary cooling step by being delivered onto a cooling ladder and allowed to flow downwardly by gravity thereon prior to being fed onto said support surface.
 8. A method as claimed in claim 2 wherein the molten sulphur is first subjected to a preliminary cooling step by being delivered onto a cooling ladder and allowed to flow downwardly by gravity thereon prior to being fed onto said support surface.
 9. A method as claimed in claim 1 including the additional step of directing cooling air onto the surface of the molten sulphur prior to contact of the sulphur with the cooling bath.
 10. A method as claimed in claim 1 including the step of directing cooling air onto the sulphur subsequent to its contact with said cooling bath.
 11. A method of solidifying molten sulphur comprising the steps of: feeding molten sulphur onto a cooling ladder and allowing the molten sulphur to flow downwardly by gravity thereon into a holding tank disposed therebeneath; selectivEly withdrawing molten sulphur from said holding tank and applying a layer thereof to the normally upper surface of a moving belt, said surface being provided with a thin layer of water sufficient to inhibit the adherence of solidified sulphur thereto; laterally tilting the support surface at selected longitudinally spaced points to cause transverse flow of the molten sulphur alternately from one side of the surface to the other; passing said layer of molten sulphur sequentially through a cooling bath to facilitate cooling and solidification of the molten sulphur; and removing solidified or partially solidified sulphur from said surface. 